Which domain do I put the SPF record in

Hi

We send out mail from our server called say mail.ourserver.com . The mail has the from address say
news <at> customersdomain.com  Ive created an SPF record in the zone file of ouserver.com which mentions the
ip address of mail.ourserver.com - do I need an SPF record in the zone file for customersdomain.com ?

Thanks in advance for help on this.

Rob Smith